Formation of reactive oxygen metabolites in the vasculature has been demonstrated during acute vascular disorders, such as ischemia/reperfusion, complement activation, adult respiratory distress syndrome, and following administration of certain antineoplastic compounds. The endothelial cells represent the primary cell type injured by reactive oxygen and this injury has been associated with increased activation and attachment of neutrophils, platelets, lymphocytes and even tumor cells to the damaged cells or to exposed basement membranes. While many studies have examined this injury, the mechanisms involved remain unclear. This is especially true of the mechanisms for loss of endothelial cell function following low levels of oxidant stress, such as that after metabolism of certain xenobiotics by the endothelium. Quinones represent an important group of compounds found throughout the environment and in many pharmaceuticals which have a propensity to cause reactive oxygen formation and cytotoxicity as they are metabolized. Recently the quinone, menadione, was shown to inhibit endothelial cell prostaglandin synthesis through a mechanism which appears to be dependent on metabolism of the quinone by the endothelial cell. Therefore, the specific aims of the proposed studies are to investigate the hypothesis that exogenous reactive oxygen species or those formed following metabolism of quinones by the endothelial cell inactive important endothelial synthetic pathways and activate intracellular signal transduction. These studies will establish optimal conditions for demonstrating reactive oxygen formation following metabolism of quinones and effective mechanisms for preventing this formation, as well as, the effects of exogenous reactive oxygen metabolites. The mechanisms for quinone-induced inhibition of endothelial cell prostaglandin synthesis will be elucidated by selectively modifying the antioxidant defenses of the cell. Oxidant-induced endothelial cell protein phosphorylation will be characterized and the mechanisms for these phosphorylations will be demonstrated by examining their dependence on second messengers and selected protein kinases. Finally, we will investigate whether a causal relationship exists between oxidant-induced inhibition of endothelial autocoid synthesis or stimulation of protein phosphorylation and increased neutrophil adherence to oxidant stressed endothelial cells. These studies will provide insight into the mechanisms for oxidant-mediated vascular injury that occurs following reactive oxygen formation within the vascular endothelial cell.